1. Field of the Invention
The present invention relates to an information management apparatus, an information management method, and a program.
2. Description of the Related Art
In recent years and continuing to the present, techniques of retrieving an image similar to a specific image from an image database using the specific image as a retrieval condition have been proposed and implemented as products.
Generally, in the similar-image retrieval techniques, a characteristic value (hereinafter referred to as a “characteristic amount”), which is obtained by the analysis of an image and serves as information for indicating the characteristic of the image, is registered at the same time as when the image is registered. In retrieving a similar image, the similarity between the characteristic amounts is calculated. If the similarity is greater than a predetermined threshold, an image corresponding to the characteristic amount is retrieved as the similar image.
As a method for extracting a characteristic amount, Patent Document 1, for example, proposes a characteristic-amount extraction technique that enables the automatic extraction of the characteristic amount corresponding to a human sense so that a human can retrieve a similar image adapted to his or her sense of similarity.
In such a similar-image retrieval technique using the characteristic amount, the characteristic amount itself is extracted in advance and stored at the time of registering an image, and a similar image can be retrieved only by the characteristic amount without reference to the image. Therefore, the retrieval of similar-image information can be executed at relatively high speed.
However, the similar-image retrieval technique described above is required to calculate the similarity between the characteristic amount and characteristic amounts of all registration images point by point at the time of retrieving the similar image. Unfortunately, processing speed for retrieving the similar image decreases as the number of registration images is increased.
In order to deal with this problem, Patent Document 2 proposes a technique in which a list of images similar to an image is retrieved in advance from an image database at the time of registering the image and is stored, and the list is used at the time of retrieving a similar image. This technique does not require the processing for calculating the similarity at the time of retrieving the similar image, which in turn can accelerate the processing for retrieving the similar image even where the number of registration images is increased.
Patent Document 1: JP-A-2000-187731
Patent Document 2: JP-A-2007-80210
The technique described in Patent Document 2 makes it possible to retrieve an image similar to a previously accumulated image at high speed, but it is not targeted for retrieving an image similar to a non-accumulated image.